Heat developable diazo photocopying sheet



United States Patent 0 3,380,830 HEAT DEVELOPABLE DIAZO PHOTO- COEYTNG SHEET Andre Schaefier and Bernard Clauss, Rueil-Malrnaison, and Michel Laquerriere, Garghes, France, assignors to Etablissemenis Bauchet & Cie, Rueil-Malmaison, France, a company of France No Drawing. Filed Sept. 21, 1964, Ser. No. 398,064 Claims priority, appiication France, Sept. 24, 1963, 948,443 2 Claims. (Cl. 96-75) ABSTRACT 0F THE DISCLOSURE A heat-developable photocopying sheet comprising a support with a light-sensitive layer on at least one side which includes a diazonium compound, an acid, and a coupling agent, said light sensitive layer having a thermodeveloping layer in chemically effective contact therewith, the developing layer including a nitrogenous carbohydrate derivative selected from a certain group or amides.

This invention relates to diazo photocopying sheets, for example for use in making contact prints of documents.

It is known that the diazo photocopying process is based on the ability of diazonium compounds contained in a diazo substance to produce dyes with coupling agents at the zones protected by the blacks of the original to be reproduced, on exposure of this substance to the light. The latent image thus obtained is then developed by contact either with gaseous ammonia or with alkaline baths which may contain the coupling agent if the latter is not incorporated originally in the diazo substance. The two methods of developing mentioned above have obvious drawbacks: the use of ammonia involves the handling of a gas with a disagreeable odour, and the use of alkaline baths often has a harmful effect on the good behaviour or appearance of the copies obtained.

To remedy the drawbacks in the above methods of developing, it has previously been proposed to provide a thermo-developing agent in a coating which is poured on the light-sensitive layer and then dried; the exposure of the light-sensitive layer to a source of heat, after exposure to light, causing the activation of the developing agent, the action of the latter on the light-sensitive layer, and then the appearance of the required copy.

The thermo-developing agent in question should, for

the purpose already mentioned, comply in particular with r the following conditions:

(a) Non-diffusion (b) Chemical inertia (0) Absence of inherent colour either in the cold or hot state (d) Absence of odour (e) Activation at a temperature as clearly defined as possible f) Absence of sticking power (g) Absence of lustre in the molten state The chief object of the present invention is to produce a diazo photocopying sheet in which the developing agent meets particularly well with the requirements stated above.

According to the present invention we provide a diazo 3,380,830 Patented Apr. 30, 1968 photocopying sheet embodying a thermo-developing agent comprising a nitrogenous derivative of a carbohydrate.

Preferably the diazo photocopying sheet comprises a support having on at least one face a light-sensitive layer containing a diazonium compound, an acid, and a coupling agent, and having a thermo-developing coating on the light-sensitive layer, said coating including a nitrogenous derivative of a carbohydrate(ose) in an organic binding agent.

The present invention is also a method of manufacturing diazo photocopying sheets, for example for use in making contact prints of documents comprising applying to at least one side of a support a light-sensitive layer containing a diazo compound stabilised by an acid and a coupling agent, and applying a thermo-developing adhesive coating to said light-sensitive layer, said coating including a dispersion of a nitrogenous derivative of a carbohydrate(ose) in an organic binding solution.

The present invention is also a diazo photocopying sheet made by the aforesaid method.

The various light-sensitive products according to the present invention are herein and in the claims referred to simply as sheets by which is to be understood paper, plates, films and the like products.

The thermo-developing agent present in the coating in the form of a pigment can advantageously be an amino carbohydrate(ose). By amino carbohydrate is to be understood a compound obtained by introducing an amino group into a carbohydrate radical by an essentially known technique.

The action of this thermo-developing agent is explained by its diffusion, at the instant of melting or softening, into the light-sensitive layer, the melting or softening being caused by the exposure of the photocopying sheet to a source of heat. Due to the effect produced by the presence of the binding agent, this softening may occur well before the real melting point of the thermo-developing agent is reached. The neutralising of the stabilising acids in the light-sensitive layer by the amino-group in the developing agent then produces the rise in the pH which is necessary to bring about the appearance of the colour.

The light-sensitive layer with which the support is provided consists in an essentially known diazo compound stabilised by an acid and a coupling agent. The layers exposure to a light source behind the document to be copied causes a latent image to form there, which is subsequently developed by exposing the sheet to a source of heat.

The thermo-developing coating is advantageously in the form of a pigment dispersed in an organic binding solution which adheres to the light-sensitive layer on the support, imparts to the coating the required viscosity to enable the coating to flow over the support, securely fixes the coating on the support and provides excellent insulation for the layer against external agents.

The organic binding solution in the coating preferably consists of a solution of a binder substance in an organic solvent which dissolves neither the constituents of the light-sensitive layer nor the developing agent.

As organic solvents meeting these requirements, the following can be cited in particular: aromatic hydrocarbons of the group comprising benzene, toluene, and the aliphatic hydrocarbon derivatives of the methylene chloride group.

Furthermore, among the binder substances which may be included in the composition of the thermo-developing coating can be mentioned polyvinyl formaldehyde, polyvinyl butyral, cellulose acetates, and ethyl celluloses.

Finally, among the thermo-developing agents of the amino-carbohydrate(ose) category more particularly meeting the requirements for their utilisation in the coating for the light-sensitive layer, can be mentioned particularly the following compounds:

M.P C. Arabinamine 98 Chitosamine 110 Glucamine 128 Glycosyl-methylamine 80 1-amino-trioxymethyl-methane 164 Mannamine 139 Galactamine 136 Rhamnasyl-methylamine (1CH OH) 127 Rhamnasyl-ethylamine (lH O) 141 Arabinyl-methylamine (211 101 Furosyl-methylamine 125 For the manufacture of light-sensitive photocopying sheet in accordance with the invention, the developing agent is preferably pulverised in such a way as to obtain grains of a size less than microns, the pulverised product then being put in suspension in an organic binder solution, the dispersion being then adjusted to a viscosity suitable for the method of spreading used, and being caused to flow over the light-sensitive layer of a photocopying paper of the type normally used to produce for instance a blueprint on developing with ammonia.

From 2 to 8 g. of developing agent are advantageously deposited per square metre of surface treated.

The invention will be better understood in the light of the following detailed description of four examples of practical embodiments of light-sensitive diazo photocopying sheets according to the invention, capable of development by heat.

Example 1 The developing agent consists of pulverised glucamine (M.P. 128 C.).

100 gr. of the pulverised compound are put in suspension in 1000 ccs. toluene in which are dissolved 50 gr. ethyl cellulose of average viscosity.

The dispersion is then allowed to flow in the form of a coating on the light-sensitive layer of a printing paper normally producing a blueprint on developing with ammonia.

Thermo-developing at about 140 C. of the diazo product thus obtained produces a blueprint.

Example 2 Chitosamine (M.P. 110 C.) is used in the same way as in Example 1. At 125 C. a blueprint is obtained.

Example 3 Furosyl-methylamine (decomposition point 125 C.) is used in the same way as in Example 1. A blueprint is obtained at 120 C.

4 Example 4 1-amino-trioxymethyl-methane (M.P. 164 C.) is used in the same way as in Example 1. A blueprint is obtained at 145 C.

Of course, the invention is in no way restricted to the foregoing examples; numerous modifications may be made by those skilled in the art, in accordance with the intended use, without thereby going beyond the scope of the invention as defined in the appended claims.

We claim:

1. A diazo photocopying sheet comprising a support having on at least one face a light-sensitive layer containing a diazonium compound, an acid, and a coupling agent, and having a thermo-developing coating in chemically effective contact with said light-sensitive layer,

said coating including, in an organic bonding agent, a nitrogenous carbohydrate derivative selected from the group consisting of:

M.P., C. Arabinamine 98 Chitosamine Glycosyl-methylamine 80 Mannamine 139 Galactamine 136 Rhamnasyl-methylamine (1CH OH) 127 Rhamnasyl-ethylamine (1H O) 141 Arabinyl-methylamine (21-1 0) 101 Furosyl-methylamine 2. A diazo photocopying sheet as described in claim 1, wherein the nitrogenous carbohydrate derivative is present in an amount between 2 and 8 grams per square meter of sheet area.

References Cited UNITED STATES PATENTS 2,318,352 5/1943 Alink 96-91 XR 3,076,707 2/1963 Lawton et al 9675 3,166,422 1/ 1965 McKinney et al. 9675 3,199,982 8/1965 Kashiwabara 9675 XR 3,284,201 11/1966 Meijs et al. 96-75 3,316,092 4/1967 Klinkowski et al. 9675 FOREIGN PATENTS 815,005 6/ 1959 Great Britain.

849,739 9/ 1960 Great Britain. 1,325,692 3/1963 France.

OTHER REFERENCES Grant, Julius, Hackhs Chemical Dictionary, 3rd ed., McGraw-Hill, New York, 1944, p. 167.

Kosar, Jaromir, Thermal Development of Diazotype Papers, Photo Science & Eng, vol. 5, N0. 2, July- August 1961, pp. 239-245.

NORMAN G. TORCHIN, Primary Examiner.

C. L. BOWERS, JR., Assistant Examiner. 

